I love wooden kayaks

April 26, 2012

Building a Cedar Strip Stand Up Paddleboard: Planking the Deck

Now for the fun part! You can get really creative by combining different woods, stripping in angles or curved patterns, or adding inlays. Katya choose to strip the deck in a simple pattern using full-length (12 ft) strips of western red cedar. The instructions recommend using strips no wider than 3 inches. Our strips are 3/4 inches wide and 1/4 inches thick. The thickness of the strips you use will depend on the softness and strength of the wood. Since some of that thickness will be lost during fairing and sanding the deck and hull, I don’t recommend using anything thinner than 3/16th inch.

In addition to being strong, lightweight, rot resistant, and easy to work with, western red cedar comes in different colors, ranging from pale yellow to chocolate brown. Clear cedar boards are usually available at your big box home improvement stores in 12 ft lengths. That’s probably the main reason I choose it over balsa or pauwlonia (which the instructions recommend) for planking.

By the time we were ready for planking, our strips had been pre-bending in the corner of the garage for several days. Inspect the strips that you plan to use to plank the deck, and pay close attention to any irregularities in thickness or defects that may have occurred while ripping them. Lay them out in the pattern you want and number them. Planking will start with placement of a central strip, and proceed by adding a strip on each side of the first strip, working out toward the edges of the board. The central strip should be no more than 1 inch wide.

Dry Heat Bending

The deck of this board is mostly flat, but has compound curves which follow the rocker of the board in one direction and the domes of the ribs in another. There is a relatively sharp upturn in the nose, which required us to make a tight bend in the nose end of each strip using a heat gun. To dry bend wood with a heat gun, secure a heat gun on a bench or have someone hold it. Turn the heat gun on high. I recommend wearing heavy leather gloves while handling the wood near the heat. Hold the strip with the area where you want it to bend between your hands and close to the gun, and bend it gently. If you need to apply heat close to the end of the strip, hold the end of the strip with a clamp instead of your hand. Thinner strips will bend easier. When the wood heats up you’ll feel it start to soften. After it is bent, the wood will hold its position. It may require a lot of heat, enough to scorch the wood, so always bend the inside surface of the wood so the scorch marks aren’t visible. I would practice this a few times with scraps of wood to get a feel for it. It works well with cedar but might not work well for other species.

I am familiar with using clamps or staples to temporarily hold strips in position while planking. The instructions describe an ingenious method using plastic wrap, specifically, Pratt Retail Specialties 5 in x1000 ft “Small Stretch Wrap”, which sells at Home Depot for about $7.97 a roll. Other brands of stretch wrap are available but, in our experience, do not have the same elastic properties as this brand, which shrinks a little after being stretched into position.

Unroll and cut out at least a yard of the stretch wrap, and take a third of it and stretch it out to double its length. Leave the other 2/3rd unstreched. Tie the stretched end to the middle of the first rib, leaving the unstretched end hanging over the side so that it is out of the way of installing the center strip. Repeat this on every other rib, tying the plastic in the middle of the rib about 6 inches away from the central spar.

Apply a thin bead of Gorilla Glue to the top of the central spar. Gorilla Glue is a polyurethane glue that requires moisture to cure, so I always wipe the wood surface with a damp rag. It expands into a space-filling foam as it cures. You will get a stronger bond with good clamping pressure. It will cure in 1-2 hours but best results come from leaving it overnight. The main reason I like to use Gorilla Glue is that it has higher temperature tolerance when cured compared to regular wood glue, which is important for those times you might leave your board in baking on a sunny beach or, more likely, strapped to the top of your car for several hours.

Set the center strip in place on the spar and check to make sure it is perfectly straight and centered. Secure the center strip by stretching the stretch wrap to thin strings like you did before and wrap them several times around the strip and spar. Tie the strings to themselves. No special knots are needed because the plastic will stick to itself. The plastic will shrink slightly and get tighter after it is tied in place.

After the glue has cured, cut off all the plastic wrap and scrape off the excess glue which will have foamed up along the sides of the strip with a knife or scraper to leave clean surfaces to glue more strips to. You will need to tie more stretch wrap to every other rib, repeating the steps you followed for the center strip.

You will need to heat bend the ends of the remaining strips to match the rocker of the nose prior to installing them. Remember to moisten the surfaces of each strip if using Gorilla Glue. Spread a thin layer of Gorilla Glue onto the edge of the strip as well as the top surface of each rib and position the strip. We also secured the ends of each new strip to the end of the center strip with clamps. Stretch the plastic wrap around the strips repeatedly in a zig-zag pattern to clamp them both to the center strip and the ribs. Pull the plastic wrap tight to eliminate any gaps between the strips.

As you add strips toward the edges of the board expect to use longer lengths of plastic wrap. It will become more difficult to reach under the spar to wrap them around the board. As the board curves downward at the edges, you might need to make a running bevel along the edges of the strips with a block plane so that the strips will fit together. We have also used short lengths of plastic packing tape or duct tape to hold strips together in areas where it has been difficult to close the gap between the strips. Duct tape is stretchier but sometimes can leave an adhesive residue.

After the deck is completely planked and the glue has cured, cut all the mounting sticks with a hand saw where they join the workbench to release the board from the bench. Have another person help lift the board from the bench and set it gently aside on the floor or another surface. Cut all the protruding remnants of the mounting sticks from the bench. Place the board back on the workbench upside down, on top of folded blankets or moving quilts or blocks placed in the middle of the workbench to keep the nose and tail from touching the bench. The board is still very flexible. The blankets or blocks placed under the middle of the board will help maintain the natural rocker in the board. It is important to try to maintain a firm and level surface for planking the hull (bottom).

Remove all the mounting sticks from the ribs and spar. The sticks should sheer or twist right off but you might have to use a knife to carefully scrape the hot glue off and avoid tearing some wood off the ribs and spar.

With the board upside down, you can see how the deck strips extend beyond the rail strips. Using a handsaw, trim the edge of the deck so it is flush with the rail strips. It does not need to be perfect at this point: we will use a block plane for fine trimming after the hull is planked. You might want to turn the board over again just to admire your handiwork. It is really starting to look like a paddleboard!